The present invention generally relates to a data communication system, and more particularly, to a method of managing property data (inherent data or attribute data) of a plurality of stations (mainly audio/video appliances) connected by an information transmission passage.
Conventionally, when data communication appliances are connected to an information communication system, the respective stations independently store and manage the property data possessed thereby, and when data is to be transferred from one station to another, the following processes are employed.
(A) Station 2 sends a property data transfer request command to Station 1, and Station 1 transfers to Station 2, the equivalent property data with respect to said command.
(B) In the case where some state variation has taken place in Station 1, Station 1 notifies all other Stations of the equivalent property data through employment of a simultaneous same report frame.
(C) When some state variation has taken place in Station 1, the content of the registered property data is transferred with respect to Stations (e.g. Stations 2 and 3) preliminarily registered in Station 1.
However, in the conventional techniques as referred to above, there have been problems as stated hereinbelow.
(i) If the above practice (A) is employed, it is difficult for Station 2 to detect in real time that the content of the property data of Station 1 has been renewed.
(ii) In the case where there are many Stations which require the property data of Station 1, the amount of processing to be effected by Station 1 is undesirably increased.
(iii) when the above practice (B) is employed, since the simultaneous same report frame is employed, responses from all Stations other than Station 1 do not enter Station 1, thus resulting in a state of effluence of property data and insufficient communication reliability, and thus, if the simultaneous same report frame is not defined for the use of the communication system, this practice can not be adopted.
(iv) If the above practice (C) is employed, many memory areas are required within Station 1, together with a simultaneous increase in the processing amount of Station 1.